The present invention relates to compositions of additives and fuels containing such compositions of additives. The present invention relates in particular to compositions of additives for diesel and/or biodiesel fuel. The present invention further relates to the use of such fuels in diesel engines to improve their performance, in particular in diesel engines with a fuel injection system of type Euro 3 to Euro 6.
Fuels that are marketed must comply with national or supranational specifications (for example standard EN 590 for diesel fuels in the EU). For commercial fuels, there is no legal obligation concerning the incorporation of additives. From the commercial point of view, in the area of fuel distribution, a distinction is made between “base price” fuels, with few or no additives, and higher-grade fuels in which one or more additives are incorporated to improve their performance (beyond the regulatory performance).
In many countries the sulphur content of diesel fuels has been subject to a very significant reduction for environmental reasons, in particular in order to reduce SO2 emissions. For example, in Europe, the maximum sulphur content of fuels of the diesel type for road vehicles is currently 10 ppm by mass. To compensate for the loss of compounds providing the lubricating character of these fuels, numerous lubricity and/or anti-wear and/or friction-modifying additives have been introduced into the fuels that are marketed. Their characteristics are broadly described in patents EP915944, EP839174 and EP680506.
As shown in FIGS. 1 and 2, it was found that when using certain higher-grade diesel fuels, deposits 1 appeared on the needles 2 of injector 3 of the injection systems of diesel engines, in particular those of type Euro 3 to Euro 6. Thus, the use of anti-wear and/or friction-modifying additives and/or additives against deposits of the coking type have sometimes displayed resistance to lacquering that is unsatisfactory, or even very inadequate. This is reflected in the formation of deposit 1 generally covered by the term lacquering, which will be used hereinafter, or using the acronym IDID (Internal Diesel Injector Deposits).
Within the meaning of the present invention, the phenomenon of lacquering does not relate to the deposits that are present outside the injection system 5 or 5′ (FIGS. 1 and 3) and are associated with coking, which is the cause of fouling and partial or complete clogging of the injection nozzles 4 or 4′ (nozzle “coking” or “fouling”). Lacquering and coking are two quite distinct phenomena both with respect to the causes of these deposits, the conditions of appearance of these deposits and the place where these deposits occur. Coking is a phenomenon that only appears downstream of a diesel injection system.
As shown in FIG. 3, the deposits 5′ formed are characterized in that they result from pyrolysis of the hydrocarbons entering the combustion chamber and have the appearance of carbonaceous deposits. In the case of high-pressure, direct-injection diesel engines, it was found that the tendency to coking is far less pronounced. This coking is simulated conventionally by the standard engine test CEC F098-08 DW10B, especially when the fuel tested is contaminated with metallic zinc.
In the case of engines with indirect injection, combustion of the fuel does not take place directly in the combustion chamber as for engines with direct injection. As described for example in U.S. Pat. No. 4,604,102, there is a prechamber before the combustion chamber in which fuel injection takes place. The pressure and temperature in a prechamber are lower than in the combustion chamber of direct-injection engines.
Under these conditions, pyrolysis of the fuel produces carbon, which is deposited on the surface of the nozzles 4′ of the injectors (“throttling diesel nozzle”) and clogs the orifices 6 of the nozzles 4′ (FIG. 3). Only the surfaces of the nozzle 4′ exposed to the combustion gases display a risk of deposition of carbon (coking). In terms of performance, the phenomenon of coking causes a loss of engine power. Lacquering is a phenomenon that only arises in direct-injection diesel engines and only occurs in the injection system.
As shown in FIGS. 1 and 2, the injectors 3 of direct-injection diesel engines comprise a needle 2, the lift of which allows precise control of the quantity of fuel injected at high pressure directly into the combustion chamber. Lacquering causes the appearance of deposits 1, which appear specifically at the level of the needles 2 of the injectors 3 (FIGS. 1 and 2). The phenomenon of lacquering is associated with the formation of soap and/or lacquer in the internal components of the injection systems of engines for fuels of the diesel and/or biodiesel type. The lacquering deposit 1 may be located on the end 4 of the needles 2 of injectors 3, both on the head and on the body of the needles 2 of the fuel injection system but also throughout the whole system for controlling needle lift (valves not shown) of the injection system. This phenomenon is particularly marked for engines using higher-grade diesel fuels. When these deposits are present in large quantities, the mobility of the needle 2 of the injector 3 fouled by these deposits 1 is compromised. Moreover, in contrast to coking, lacquering may also cause an increase in engine noise and sometimes problems when starting. In fact, the parts of the needles 2 fouled by the deposits of soap and/or of lacquer 1 may stick to the inside walls of the injector 3. The needles 2 are then blocked and the fuel no longer passes through.
Deposits of the lacquering type are generally divided into 2 types:
1. deposits that are rather whitish and pulverulent; on analysis, it is found that these deposits consist essentially of soaps of sodium (sodium carboxylates, for example) and/or of calcium (type 1 deposits);
2. organic deposits like coloured lacquers located on the body of the needle (type 2 deposits).
Regarding the type 1 deposits, there may be several sources of sodium in biodiesel fuels of type Bx:                the catalysts for transesterification of vegetable oils for producing esters of the type of (m)ethyl fatty acid esters such as sodium formate;        sodium may also originate from the corrosion inhibitors used when conveying petroleum products in certain pipes, such as sodium nitrite;        finally, accidental exogenous contamination, via water or air for example, may contribute to the introduction of sodium into fuels (sodium being a very common element).        
There are several possible sources of acids in fuels containing bio diesels, for example:                the residual acids of the biofuels (see standard EN14214, which stipulates a maximum permitted level of acids)        the corrosion inhibitors used when conveying petroleum products in certain pipes, such as DDSA (dodecenylsuccinic anhydride) or HDSA (hexadecenylsuccinic anhydride) or certain of their functional derivatives such as AmaAmaacids.        
Regarding the type 2 organic deposits, certain publications state that they may in particular originate from reactions between deposit reducing agents/dispersants used for preventing coking (for example detergents of the PIBSI type derived from polyamines) and acids (which would be present among other things as impurities of the fatty acid esters of the biodiesel). In the publication SAE 880493, Reduced Injection Needle Mobility Caused by Lacquer Deposits from Sunflower Oil, the authors M. Ziejewski and H. J. Goettler describe the phenomenon of lacquering and its harmful consequences for the operation of engines using sunflower oils as fuel. In the publication SAE 2008-01-0926, Investigation into the Formation and Prevention of Internal Diesel Injector Deposits, the authors J. Ullmann, M. Geduldig, H. Stutzenberger (Robert Bosch GmbH) and R. Caprotti, G. Balfour (Infineum) also describe the reactions between acids and deposit reducing agents/dispersants to explain the type 2 deposits.
Moreover, in the publication SAE International, 2010-01-2242, Internal Injector Deposits in High-Pressure Common Rail Diesel Engines, the authors S. Schwab, J. Bennett, S. Dell, J. Galante-Fox, A. Kulinowski and Keith T. Miller explain that the internal parts of the injectors are generally coated with a slightly coloured deposit that is visible to the naked eye. Their analyses enabled them to determine that this was predominantly sodium salts of alkenyl-(hexadecenyl- or dodecenyl-)-succinic acids; the sodium originating from drying agents, from caustic liquor used in the refinery, from tank bottom water or from seawater, and the succinic diacids being used as corrosion inhibitors or present in multifunctional additive packages. Once formed, these salts are insoluble in low-sulphur diesel fuels and, as they are in the form of fine particles, they pass through the diesel filters and are deposited inside the injectors. In this publication, the development of an engine test is described and allows the deposits to be reproduced.
In the publication SAE International, 2010-01-2250, Deposit Control in Modern Diesel Fuel Injection System, the authors, R. Caprotti, N. Bhatti and G. Balfour, also investigate the same type of internal deposits in the injectors and assert that the appearance of deposits is not connected specifically with a type of fuel (diesel or containing biodiesels) nor with a type of vehicle (light vehicles or lorries) equipped with modern engines (common rail). They show the performance of a new deposit reducing agent/dispersant, effective on all types of deposits (coking and lacquering).
Accumulation of deposits of the lacquering type as described above may lead to the following problems:                a slowing of the response of the fuel injector,        sticking of the internal components, which may lead to a loss of control of the injection time as well as of the quantity of fuel supplied per injection,        a deterioration in the driving pleasure of the vehicle,        variations of power,        an increase in fuel consumption,        an increase in pollutants,        disturbance of combustion, since the quantity of fuel injected will not be what is envisaged theoretically and the injection profile will be different,        unstable idling of the vehicle,        an increase in noise produced by the engine,        a decline in the quality of combustion in the long term,        a decline in the quality of atomization.In the case when there would be a heavy deposit of the lacquering type, the vehicle could have great difficulty starting, or even may no longer start at all, since the needle allowing injection would be blocked.        